On mine, I was able to grind the head of the rivet down with a angle grinder. Then I took a center punch and made a punch mark in the middle of the rivet. I even drilled off center on a few and the trunnions didnt egg shape, they are really hard. I got all of mine out this way and it was pretty easy. On the long ones I drilled halfway and then flipped it and drilled the rest of the way from the other side. I started with a 1/8 and then I worked up to a 5/32 or a #21 using a hand drill really slowly and a lot of pressure. The rivet will then break loose and spin and then you can push it out.